Research on Carbon Emission Accounting for Tunnel Exit Slope Construction Based on 3D Terrain Reconstruction

Under the "dual-carbon" strategy， controlling carbon emissions during the tunnel construction phase has become critical for the low-carbon transition of transportation infrastructure. To address the limitation of traditional design-drawing-based methods， which cannot accurately reflect on-site construction conditions， this paper proposes a high-precision carbon accounting method based on three-dimensional（3D） terrain reconstruction. A 3D site modeling approach using UAV oblique photogrammetry and multi-view geometric reconstruction was developed to enable accurate extraction of the disturbance area and earthwork quantities. Based on the 3D terrain data， a multi-dimensional carbon accounting framework was established， covering mechanical operations， material transportation， and vegetation disturbance， thereby enabling precise estimation of construction-phase carbon emissions and facilitating construction scheme optimization. The proposed method was applied to a tunnel project on the Xi’an-Chongqing High-Speed Railway. The baseline scheme （Scheme 1） yielded 355296.6 kgCO₂e. Two optimization schemes were further proposed： Scheme 2 reduced emissions by 33.83% by eliminating high-energy equipment and optimizing construction scheduling； Scheme 3， building on Scheme 2， reduced emissions by 34.31% by optimizing equipment configuration， improving machinery efficiency， and introducing photovoltaic power. At the same time， the optimized schemes reduced total construction cost from CNY 2.5517 million to CNY 2.0887 million.